Trict op coxumbia



Ang. 18, 1925,

1,550,335 F'. G. BENEDICT ET AL APPARATUS FOR MEAsURINGv OXYGEN CONSUMPTION 1N THE STUDY 0F METABOLISM Filed April 17. 1924 clnvervl: o16

Patented' Aug. 18, 1925.

UNITED STATES PATENT OFFICE.

FRANCIS G. BENEDICT AND COBNELIA GOLAY BENIDJICT, I' BOSTON, IASBACHUSFI'T,

ABSIGNOBS T0 CABNMIE INSTITUTIONOF WASHINGTON, 0'! WASHINGTON,- DIS- TBICT OF COLUMBIA, A CORPORATION INCORPORATED BY ACT Ol' CONGRESS Ol' m UNITED sturm.

.APPARATUS FOB IEASURING OXYGEN CONSUMPTION IN THE STUDY OI HETALBOLISH.

Application mea April 17, 1m. ,semi no. 707,156.

To all 'whom it may concern.' y

Be it known that we, FRANCIS G. Bann- DIc'r and CORNEIJA GoLAY BENEnrc'r, citizens of the United States, residing at Boston, in the countyof Sufolk'and State of Massachusetts, have invented certain new and useful Improvements in Apparatus for Measurin vOxygen Consumption in the Study of etabolism; and we hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, which form part of this specification.

This mvention is a novel improvement in methods'of and apparatus for use in the study of metabolism; and is especially adapted for measuring the consumption of oxygen b human beings.

Two filindamental methods of gaseous metabolism measurements are possible for general laboratory usage; (a) the determination of the oxygen .absorbed outl of a closed, circulating volume of oxygen-rich air, and (b)the separation of the'inspired and expired air, collection of the expired air, and analysis of samples of this air. Apparatus for performing the first method usually costs several hundred dollars, and the apparatus employed inv the second method is fully as expensive as the closedcircuit apparatus. But the great draw;- back from the `pedagogical standpoint is the length of time required in the gas analysis method to clean and assemble apparatus, provide the reagents, test, and make a good gas analysis.

The uses of the measurements of gaseous metabolism are twofold: First, ythey impart a knowledge of the composition of the outdoor air and the expired air, the volume of respiration per unit of time, the calculation of the amount of oxygen consumed and.

carbon dioxide produced per unit of time, and the relatiol between the volumes of 'carbon dioxide, and oxygen, i. e., the respiratory quotient, which is of great si icance as an index of the character o the material being burned in the body. Second, the ossib-ility of computing therefrom the totalP metabolism. Pedagogically, all

the factors above mentioned are of eat significance, but practically in clinica use.

only., one is of great importance, i. e., the oxygen consumption, for from this is computed the heat production which under known conditions, such as complete vmuscular repose and in the post-absorptive state, is characterized as the basal metabolism. Knowledge ofthe basal metabolism is of the greatest practical value not only in the study of the disturbances ofthe ductless glands but also as an index of general tone.

Une object of the present invention is to provide a simple, portable, accurate and inexpensive apparatus for the measurement of the oxygen consumption alone; which apparatus can be readily carried around, and by which the amount of oxygen consumed from a definite volume of oxygen-rich air can be determined without any sacriice of accuracy -in results to facility of operation; the apparatusbeing operated by our novel method of measuring oxygen consumption by the use of such apparatus, as hereinafter explained The apparatus in brief comprises a reagent container with an elastic, readily expansible cap, valved tubesconnecting the container with a mouthpiece; and a pump to supply quantitatively. oxygen or air to the container. In use the subject inhales air through the mouthpiece from the container and exhales air through the mouthpiece back into the container, and the exhaled air passing through soda-lime in the bottom of the container is deprived of its carbon dioxide and can then be rebreathed. The elastic rubber cap permits large changes in volume with each respiration, as well as a gradual decrease in volume'due to the absorption lof oxygen in the lungs of the subject. 'The amount of decrease in volume ina unit of time is the measure desired.

If at the start there is only ordinary air in the container the absorption of oxygen would be so rapid that a normal adult subject would, in a few minutes, reduce the oxygen percentage to a. int where the subject-would actually exhi it signs of oxygen want. It has been found that there is no measurable difference in oxygen consumption, whether the subject is breathing ordinary air, or air enriched with from, 80 $.90 per cent of oxygen. Therefore the air'in the container is preferably enriched with pure oxygen, before using the apparatus and the amount of oxygen absorbed out of the confined volume of oxygen-enriched. air can be readily determined by introducmg into the container a measured amount of ordinary room air.

To enable others to clearly understand and use the invention, we will describe the apparatus and method with reference to the accompanying drawings, which illustrate a practical, simple, portable apparatus by which the total volume of oxygen absorbed during a certain period can be readily determined and in the claims following such description we have set forth the essentials of the invention and the novel features of construction and novel combinations of parts for which protection is desired.

In the drawings:

Figure 1 is a side elevation, partly 1n section, of a complete apparatus embodying the invention. i t h Figure 2 is an enlarged detail sectional view of the three-way valve.

Fig. 3 is an enlarged detail sectional view of the mouth piece.

Fig. 4 is a detail sectional View of the pump piston.

The apparatus shown comprises a simple can or container l having an elastic cap 2, preferably made of thinl sheet rubber which will readily expand or contract under slight variations of pressure and will act as. a yielding variator of the volumetric capacity of the container. In the container is placed a quantity of a suitable reagent such as soda-lime indicated at R.

The upper part of the container, above the reagent, is connected by an' inhaling tube 3 with a tube 4 to which is connected a mouth piece 9. Said tube 4 is also connected by an exhaling tube 5 with the lower end of the container 1, below the reagent therein-' The tubes 3 and 5 may be of rubber.

A valve 3m is interposed between the tube 3 and the container 1 to permit air from the container to be inhaled through the tube 3, and prevent exhaled air passing back through tube 3 into the container. A valve 5a is also interposed betweenthe tube 5 and the container to permit exhaled air to .enter into the container 1, and prevent air being withdrawn from the container through tube 5.

Atmospheric air may be admitted into the container 1 through an inlet pipe 6 connected to a 3-way valve 6a. This valve 6a is also connected by a tube 7a, preferably of rubber, with an air pump 7, by which a measured uantity of air can be forced through v ve 6m (when properly adjusted) and pipe 6 into the container 1.

The valve 6a is also connected byl a pi e 8a with a calcium chloride tube 8 of ordinary construction as indicated in Fig."1. By properly adjusting valve 6a dry room air can be first drawn through ipes 8m and 7a into the pump 7 and then, a r properly shifting valve 6m, such air can be forced from the pump into the container.

To the pipe 8m is attached a rod 8c which carries a clamp 8d through which extends an adjustable indicator rod or needle 2e arranged directly above the cap 2, and which serves as an indicator or index to show the degree of distension of the cap 2, as hereinafter explaine The aforesaid parts are preferably constructed as follows:

The reagent container 1 may be an open top can of copper, galvanized iron or tin. The cap 2 may be of elastic gum or rubber. In practice, an ordinary pure-gum bathing cap makes a simple andentirely satisfactory cap or expansion chamber. Such caps have an opening which can be readily stretched over the top endvof the container and it can be held firmly in place by an ordinary rubber band 2a, and make an absolutely gas ltight joint between the cap 2 and the upper portion of the container. Care must be taken to prevent any leak at such point.

To aid in noting the exact height or point of distension of the cap 2 a light-weight disk 2o, of any suitable material, is cemented or otherwise attached to the top center of the cap; and said disk is adapted to contact with the lower end of the adjustable rod or needle 2e.

As shown there are four openings in the wall of the container. In two are secured standard brassbushings, 1. 1b t0 which are respectively connected the casings 3h 5h of the valves 3a, 5a. To stifen the connection a nut 1n is screwed onto the tion of the bushing 1a inside the container, and a Washer 1., curved to fit the container is interposed between the nut and the inner wall of the container. j

To the lower bushing 1b within the container is screwed atube 5b having a slot in its lower side extending about one-half of its length.

In a third opening, above the level of the reagent R, is secureda standard brass bushing 10 to' which the pipe 6 is attached. And to the fourth opening is connected a petcock 11 through which oxygen can be admitted to enrich the air in the container when desired.

The 3-way valve 6a is of standard size, and so constructed that the plug 6b can move a quarter turn. The central outlet of the valve (see Fig. 2) connects with the pipe 6;

threaded por-` llO the u per outlet connects with the pipe 8a; and t e lower outlet connects with thel tube 7a. A handle 6c is attached to the plug 6b of the valve in such a way that-w en the handle is .upright as in Fig. (and as 1ndicated in dotted lines '60, in Fig. 2) the calcium-chloride tube 8 will bc connected to the air pump 7. When the handle is in a horiwar gas masks. On a gas maskno `special housingffor the'valve 1s necessary, but in our apparatus the Sadd valves are enclosed in simple housings, preferably .of brass, in-l dicated at 3h and 5,..

The exact type of respiratory valve employed is'not an essential of the invention; nor is the form of the housing thereof.

The tubes 3 and 5 are preferably of rubber, so they can be readily connected tothe valves and the'tube- 4.` Y

`The tube 4 has at its upper end a portion 4c extending at ri ht angles to the longi` tudinal axis thereof and to this en d is .connected one endy of the tube 3. Below the portion 4c is a portion 4d extending parallel with 4c, to which is connected one end of l the tube 5. Tube 4, and portions '4c and 4d thereof are preferably constructed of suitable lengths of thin brass tubing soldered together at the joints. To the lower open end of the tube 4 is connected a suitable mouth piece. through which the Apatient breathes during the operation ofthe apparatus. In the tube 4 may be inserted a moistening device of anysuitable kind. ,We

preferably use .a small loosely fitting cylinder of brass gauze covered with cotton orv linen fabric which is thoroughly drenched with water before using the apparatus.

The tube 4 and mouth piece may be conveniently suspended from a rod or pipe 10b attached vby a swingable joint 10c, of any suitable construction, to an upright rod or pipe 10 which may be detachably attached in any suitable lmanner `to the base B on which the entire apparatus canbe mounted, as indicated in Fig. 1. The upright 10 can be unscrewed from the base when it is desired to transport the apparatus. When iny use the member 10b canbe swung toright or left, and the tube 4 can be suspended' from the rod 8b in any convenient manner.

In the drawings the tube 4 is shown as provided with a ring 4e' slidably mounted on A I'Od 10b.

' factory pump.

'u A short thin walled tube 9a, preferablyof brass, and having a ilange or ring 9b on one end is slipped through an opening in a rubber.. shield 9. The tube 9 and ring 9b should be nickelplated, or otherwise treated to prevent corrosion. The shield 9 is preferably 'out from a piece of heavy sheet rubber, in an oval form and has a hole in its-center slightly smaller in diameter than the tube 9,v to make va close joint therewith. The rubber shield 9 is of such size that it can be conveniently held in the mouth between the lips and the teeth. A short length of soft rubber tubing 90 connects the part 9 of the mouth pice with vthe lower end of tube 4. The combination of nickel-plated tube 9a and rubber shield 9 has the advantage of vbeing easily cleaned and the expense of de terioration of a speciallyvmoulded mouth piece is done away with. The particular kind of mouth piece used however isofl secondary importance.

To measure exactly the amount of air introducedto'replace the oxygen used by the subject requiresa calibrated instrument delivering known volumes of air. As no particular pressure is required a wellv made pistonpump 7, such asan'automobile pump, can be used;fone having alreasonably large barrel and a short stroke of piston is of` practical advantage. We have found an automobile grease gun makes a very satis- `Preferab1y thevpistonjof the pump (see l Figs. 1 and 4) is composed of oppositely disposed leather cup washers 7a separated'byV 'an interposed metal disk 7 b, and supported by exterior metal disks 7c the whole being I tightly secured together and to 'the piston rods 7e by a nut 7d.

It is of vital importance that the piston be well lubricated,- and closely. fit the barrel at all times, so' that there will b e no opportunity for air to leak varound or through the piston rod.- A most excellent lubricator is. mutton tallow. A11 invariable length of stroke of the piston is necessary, and a simple method of insuring this is to place a short metal collar 7h, on the piston rod inside of the cylinder and a likeV collar 7c' on the piston rod outside of the cylinder. Then when thepumphandle is drawn out the collar 7h on the inside comes in contact with the head of the cylinder so that the soft leather of the piston is not touched; and when the piston is pushed inward the collar '7'strikes the cylinder head before any part of the piston touches the other head of the cylinder. The length of stroke is regulated by `such collars; and by changing the length of the collars 7h, 7e' the length of stroke can be varied. -v

The exact amount of air discharged for each full reciprocation of the pump piston must be actually determined before the apparatus is actually used; and when so determined the exact amount of air forced into the container by the pump during use of the `apparatus can be readily ldetermined and be absolutely air tight. When the apparatus is set up entirely ready for use, a rubber stopper should be placed in the mouth piece and the rubber.A cap distended toa moderately roundedform, and the index needle 2e adjusted until its lower end just touches the disk 20. The degree of convexity of the cap is a rather important point kin respiration experiments. As the cap is filled with air there is obviously a vertical as well as a lateral displacement of the cap, but when the cap is nearly filled, there will be a point where each millimeter in vertical displacement will correspond to about 5 to 10 cubic centimeters of air in the pump. That is, a movement of the piston of 3 to 5 millimeters will produce an elevation of about l millimeter of the disk 2e. This is the ideal point for beginning and ending respiration tests. After setting the cap a weight of 35 to 50 grams should be placed on top `of the cap and allowed to stand for three minutes. If

any appreciable leak is present, it will be indicated when the weight is removed, and the position of the index needle and the disk noted. If a leak is noted, it may be either in the valves or around the container and cap.

The valves can be tested' while still attached to the rubber tubes by placing stoppers in the open end of each valve housing,

immersing them in a pail of water, and blowing through the mouthpiece. The reagent container and cap can be tested alone by putting rubber Stoppers in the pipes connecting with the container. By turning the S-way valve the entire system may be tested at one and the same time, and if the apparatus shows no leak it is ready for use.

The usual prerequisites for the conditions of basalI metabolism measurements are that the patient has had a preliminary period of rest, that there is absence of psychical activity or any febrile temperature; and particularly that the patient is in the post-absorptive condition. All these bein assured, the operation would proceed as fo ows:

After placing a suitable moistener in the .tube 4 the mouth piece is attached thereto.

The containenis then supplied with oxygen from a suitable container through the petcock 11, beginning admission of oxygen while the cap 2 is fiat or slightly depressed into the container. This insures enough oxygen enrichment to preclude lany possibility of oxygen want.

A suitable nose clip is then placed on the patients nose, preferably at the Vend of a normal expiration. When the operator does this it is helpful to watch the rise and fall of the chest of the patient.` Any nose clip may be used but we prefer the Siebe-Gorman nose clip. 4

The cap 2 will now rise and fall with each respiration of the patient. Enough air should then be introduced into the container by the air pump to cause the cap 2 to expand until the disk 20 touches the needle 2e, and preferably until the cap /bulges slightly around the top of the container. Great excess is undesirable, as it is liable to produce pressure against which the subject must exhale.

At the end of each successive expiration the disk 2c will press less and less against the needle 2e and shortly it will just touch. At this point a stopwatch should be started; or the exact time noted on 'an ordinary watch, recording first thev position of the second hand, then the minute and hour.

should first be pushed fully inward; then valve 6a should be turned so as to connect the pump 7 with the calcium-chloride tube 8, and then the pump piston drawn completely out. The valve 6a should then be turned to connect the pump 7 with the container and then the pump piston slowly pushed in forcing the perfectly dry air from the pump into the container.

The air ump 7 should then be again filled with ry air (as described) and slowly forced into the container. Any major movements of the plunger should bemade when .the cap is high, i. e., towards the end of expiration, to avoid introducing an excessive amount of air into the bag.

As the piston nears the end of a complete expelling stroke (forcing air out of the pump) the` excess of air in the container slightlyr distends the cap.; then wait, as at the start (see above), contacts the needle. Note the time but do not stop the watch. Record the time Vrequired for the introduction of air in one complete expelling stroke of the piston, in minutes and seconds.

Repeat the above o eration for six full expelling strokes of t e piston, notingthe total elapsed time` in each case.

until the disk 2c just y pressure.

At the end .of the sixth expelling stroke, after noting the time, remove the nose cllp and mouth piece; record the temperature of the pump and the barometrlc pressure: The temperature of the pump can be obtained by an ordinary laboratory thermometer, with its bulb touching the brass of the barrel.

The apparent volume o f oxy en absorbed during the complete eriod w en six full expelling strokes of t e pum piston-were introduced is computed readi y. From .the internal diameter of the barrel and the length and number of lexpelling strokes the apparent volume of air .introduced 1s.co m puted; and obviously the volume of air 1ntroduced would be constant for any given air pump. There is no tension ot aqueous vapor to be considered, for the air drawn into the ump is dried by calc1um chloride, in the tube 8 and thus the apparent volume may be reduced to 0 C. an 760 mm. by the formulalf y l y 273-' p ,VX273 :X760 in which t is. the temperature of the pump barrel and p the observed barometric pressure. The gases increase in Volume l/273 for each degree rise in temperature, and the volume increases with decreasing barometric Car nters standard tables glv- 1n the com ined factor for reducing vo umes of dry air to 0 C. and 760 mm. may `be used in calculating results.

Finally, if thereduced volume be dlvided by the timek in minutes, the .oxygen con-- sumption r minute is obtained. The calculation t uspis more simply expressed as .obviously K may bealtered to include any number of'strokes.`

While the nal time, (i. e., the time required to make the six full expelling strokesmay-be taken as the measure of the metabo ism and the oxygen'romputed directly therefrom; it is obvious thatgth1s time is computed'from but two readm i. e., that at the beginnin and that att eend of theex eriment. e error in reading is norma y very slight.

Rarely should the disk 2., be farther than 1 millimeter from the' index needle' atthe time of reading, i. e., a difference represent-- ing hardly .10 c. c. Almost invariably it will be very much less than that. But there bean abnormally .shallow or abnor-v ma may deep lres iration just at the beginning or end. uch respirations would eftion per minute, as outlined above, is of strokes,` m 1s the reduction I expelling piston stroke.

The measurement of the oxygen consumpvalue chieiiy as furnishing the means for the direct computation of the heat production. Each liter of oxygen absorbed in metabolic transformations 1s accompanied by the liberation of approximately 5 calories of heat. The exact calorilic value of a liter of oxygenvaries from 4.686 to 5.047, varying directly as the respiratory` quotient. The

fled, a reagent container having a substantially non-resistant expansive portion; a mouth piece; an lnhaling tube connecting the container with the mouthpiece; an exhaling tube connecting the mouth piece with the container; means to prevent inhalation through the exhaling tube, and exhaling through the inhalation tube; means for admitting a measured volume of dry air into the container; and means coacting with said expansive portion to indicate variations in 10 the volume of air in the container. Y

2. In an apparatus of the character, specified, a reagent container having a substantially' non-resistant expansive portion; a mouth piece; an inhaling tube connecting the upper portion of thecontainer with the mouth piece; lan exhaling tube connecting the mouth piece with the container; means to prevent inhalation through the exhaling tube, and exhaling through the inhalation tube; an air measurin pump; means for controlling the admisslon of-air from the pump to the container; means to desiccate the air supplied to the pump; and means coacting wlth said expansive portion to indicate variation in the volume of air in the container.

3. In an apparatus of the character specified, a reagent vcontainer having a substantially non-resistant expansive portion; a mouth piece; an inhaling tube connecting the upper portion of the container above the reagent with the mouth piece; an exhaling tube connecting the mouth piece with thev container below the reagent therein;

valves to prevent inhalation through the exhaling tube, and exhaling through the inhalation tube; means for admitting oxygen to the container; means for supplying a measured volume of dry air container; means for controlling the' admission of dry air from the supply to the container; and means coacting With said expansive portion to indicate variations in the volume of oxygenated air in thek container.

4. In an apparatus of the character specified, a reagent container having a substantially non-resistant expansive portion; a mouth piece; an inhaling tube connecting the container With the mouth piece; an exhaling tube connecting the mouth piece with the container; valves to prevent inhalation through the exhaling tube, and exhaling through the inhalation tube; means for admitting excess oxygen to the container; an air measuring pump; a tube for conducting air from said pump into the container; a

valve for controlling the admission of air from the pump to the container; means to desiccate the air supplied to the pump; and means coactingwith said expansive portion to indicate variation in the volume of air in the container.

5. In an apparatus of the character specified, a reagent container having an elastic expansive cap; a mouth piece; an inhaling tube connecting the container With the mouth piece; an exhaling tube connecting the mouthpiece with the container; means to prevent inhalation through the exhaling tube, and exhaling through the inhalation tube; means for supplying a measured volume of dry air into the container; means for controlling the admission of dry air from the supply to the container; and means coacting with said expansive cap to indicate variations in the volume of air in the container.

6. In an apparatus of the character specied, a reagent container having an elastic expansive cap; a mouthpiece; an inhaling tube connecting. the container With the i mouth piece; anl exhaling tube connecting the mouth piece with the container; valves to yprevent inhalation through the exhaling tube, and exhaling ythrou'gggh the inhalation tube; an air measuring pump; a tube for conducting air from said pump into the container above the reagent therein; a valve for controlling the admission of air from the pump'to the container; means to desiccate the Vair supplied to the pump; and means coacting with said ca to indicate variation in the volume of air in the container.

7. Apparatus of the character specined comprising a reagent container having a non-resistant `elastic cap; a mouth piece tube; an exhaling tube; an inhaling tube connecting the mouth piece tube with the container; valves tol prevent inhalation through the exhaling tube, and exhaling through the inhalation tube; a pump, means for admitting a measured volume of dry air from the pump into the container; a valve for controlling the admission of air to the pump, and from the pump to the container; means for admitting excess oxygen into the container; and an adjustable indicator coacting with said cap to indicate variations in the volume of air in the container.

8. Apparatus of the character specied comprising a reagent container havin a non-resistant elastic cap; a mouth piece tube; an inhaling tube connecting the upper portion of` the container above the reagent With the mouth piece tube; an exhaling tube connecting the mouth piece tube with the container below the reagent therein; valves to prevent inhalation through the exhaling tube, and exhaling through the inhalation tube; a chlorinator; an air measuring pump; a tube for conducting air from said pump into the container abovethe reagent therein; a valve for controlling the admission of air from the chlorinator to pump and from the pump to the container; means for admitting excess oxygen to the container; and an adjustable indicator coacting with said cap to indicate variation in they volume of air in the container.

In testimony that We claim the foregoing as our own, We afiix our signatures.

FRANCIS G. BEN EDICT. CORN ELIA GOLAY BENEDICT. 

